Genes&Dev:中科院遗传李云海研究组等揭示DA1调控植物种子和器
2017年2月6日，国际遗传发育与分子生物学经典期刊《Genes & Development》杂志上在线发表了英国约翰英纳斯中心Michael Bevan教授研究组和中国科学院遗传与发育生物学研究所李云海研究组合作的一篇研究论文，研究论文报道了揭示DA1调控植物种子和器官大小机制。董慧、Jack Dumenil、Fuhao Lu、李娜等为共同第一作者，Michael Bevan和李云海为共同通讯作者。
植物种子和器官大小是重要的农艺性状，种子和器官大小的调控也是重要的发育生物学问题。李云海研究组的前期工作表明，泛素受体蛋白DA1与两个E3泛素连接酶DA2和EOD1/BB直接互作，协同调控种子和器官大小(Li et al., Genes & Development 2008; Xia et al., Plant Cell 2013)。此外，DA1通过介导去泛素化酶UBP15/SOD2以及转录因子TCPs蛋白的降解调控种子和器官大小(Du et al., Plant Cell 2014; Peng et al., Plant Cell 2015)。但是，DA1与两个E3蛋白协同作用的机制以及DA1介导底物降解的机制仍不清楚。
研究发现了泛素受体DA1具有蛋白酶活性，E3泛素连接酶能够激活DA1蛋白酶活性，并通过切割下游底物调控种子和器官大小的重要机制。DA1含有两个保守的泛素结合区、一个LIM结构域和一个C端蛋白酶结构域。E3泛素连接酶DA2和EOD1通过泛素化DA1，激活了DA1的蛋白酶活性。活化的DA1可以切割UBP15，TCP15，TCP22等下游底物。因此，该研究揭示了DA1的蛋白酶活性通过协同调控下游底物的稳定性调控种子和器官大小的重要机制。
具有蛋白酶活性的泛素受体DA1调控种子和器官大小的分子模型
原文链接：
Ubiquitylation activates a peptidase that promotes cleavage and destabilization of its activating E3 ligases and diverse growth regulatory proteins to limit cell proliferation in Arabidopsis
原文摘要：
The characteristic shapes and sizes of organs are established by cell proliferation patterns and final cell sizes, but the underlying molecular mechanisms coordinating these are poorly understood. Here we characterize a ubiquitin-activated peptidase called DA1 that limits the duration of cell proliferation during organ growth in Arabidopsis thaliana. The peptidase is activated by two RING E3 ligases, Big Brother (BB) and DA2, which are subsequently cleaved by the activated peptidase and destabilized. In the case of BB, cleavage leads to destabilization by the RING E3 ligase PROTEOLYSIS 1 (PRT1) of the N-end rule pathway. DA1 peptidase activity also cleaves the deubiquitylase UBP15, which promotes cell proliferation, and the transcription factors TEOSINTE BRANCED 1/CYCLOIDEA/PCF 15 (TCP15) and TCP22, which promote cell proliferation and repress endoreduplication. We propose that DA1 peptidase activity regulates the duration of cell proliferation and the transition to endoreduplication and differentiation during organ formation in plants by coordinating the destabilization of regulatory proteins.
作者：李云海
